giovedì 11 dicembre 2008

I want to thank Jason Vertrees for the following collection of useful tips!

(1) Use ~/.Rprofile for repeated environment initialization

(2) Ever have the problem of a large data frame only being displayed across 40% of your terminal window? Then, you can resize the R display to fit the size of your terminal window. Use the following "wideScreen" function:

(3) Get familiar with colorspace. For example, if you need to color data points across a range, you can easily do:
##
## lut.R -- small function that returns a cool pallete of nColors
##
require(colorspace)
lut <- function(nColors=20) {
return(hex(HSV(seq(0, 360, length=nColors)[-nColors], 1, 1)));
}
# Now use lut.
plot( rnorm(100), col=lut(100)[1:100] )
# Now use just a range; use colors near purple; pretty
# much like gettins subsections of rainbow.colors()
plot( rnorm(30), col=lut(100)[71:100] )

(5) A _VERY_ useful tip is to show the users the vast difference in speed between using for, apply, sapply, mapply and tapply. A for loop is typically very slow, where the ?apply family is great. You can use the apply vs for-loop in the neighbors function above with a timer on a large set to show the difference.

(6) Another useful tip, also in neighbors is generating difference vectors and their lengths:
# the difference vector between two vectors is very easy,
c <- a -b
# now the vector length (how far apart in Euclidean space these two points are)
sqrt(sum(c**2))

mercoledì 3 dicembre 2008

I know that the best/recommended way to manage the authoring of R code consists in building a package containing a DESCRIPTION file.
Nevertheless, I wrote a very basic function retrieving the name of the authors of a script (or any text file) if these names are written within the first three rows of the file (easily changeable) with this format: